Conventional imaging systems (e.g. digital cameras, camera phones, camcorders and other imaging devices and applications) typically incorporate a camera lens module as part of the system assembly. This lens module is comprised of a focal plane array, a mechanical housing, an optics assembly, and an electrical interface with connector.
FIG. 1 illustrates an exemplary conventional motor driven lens module 100 (module case represented by dashed line). The lens groups (focus lens group 102 and zoom lens group 104) within the lens module 100 are illustrative only, as it should be understood that many different configurations of lenses may be used within the lens module 100. For example, if the lens is a fixed or prime lens, then only one or more focus lens groups are present and move for focusing. If the lens is a zoom lens, then the lens groups act together to provide the zooming function, and one or more focus lens groups move for focusing. Additionally, one or more lens groups may be moved for temperature compensation, image stabilization, and anamorphic distortion.
A lens group is comprised of one or more lens elements with a primary purpose of altering the path of electromagnetic radiation. Elements of a lens can be made from many differing types and compositions of materials, examples of which include glass of various compositions, crystals, plastics or resins, ceramics, liquids, or even a combination. Additionally, lens elements can be reflective, such as a mirror or prism. The elements of a lens can be made into different shapes, thicknesses, or other properties and can be made and/or combined with other elements to perform various tasks including focusing, magnification, reduction, reflection, refraction, correction or creation of regular distortion (including anamorphic distortion) and correction of lateral color. By altering the position, shape, transmittance, reflectance, magnetic attraction, or other properties of the elements, the functions described above may be performed. For example, moving an element along an axis perpendicular to the focal plane array 108 (along the primary or optical axis) is useful to provide focus and/or zoom capability. Similarly, changing the shape of a liquid or pliable element and/or in combination with moving it can do the same. Moving or changing the shape of an element relative to and along the primary axis is useful to provide image stabilization and temperature compensation. Sensors may be employed to sense some property of the lens elements such as position, shape, temperature, magnetic flux, displacement, humidity, and light. Some example embodiments of lens sensors include linear or rotary encoders, displacement sensors, thermistors, thermocouples, counters, motion detectors, and accelerometers.
The lens groups of FIG. 1 focus the visible electromagnetic spectrum or the infrared electromagnetic spectrum onto an image sensor (e.g. focal plane array) 108 within the lens module 100. A focal plane array is a device containing one or more elements that detect or sense electromagnetic radiation at various wavelengths or in ranges of wavelengths. These elements can be tuned through a variety of means to sense or detect, for example, the human visible light spectrum as would be used in digital photography and video. They can also be tuned to sense or detect infrared light, ultraviolet light, or other desired wavelengths or bands of wavelengths. Some example embodiments of focal plane arrays include charge coupled devices (CCDs), Complementary Metal Oxide Semiconductor (CMOS) active pixel sensors, CMOS active column sensors, quantum dot focal plane arrays, and gallium arsenide infrared arrays. Examples of focal plane arrays are found in U.S. Pat. No. 6,084,229, U.S. Pat. No. 5,471,515, and U.S. Pat. No. 4,054,797, the contents of which are incorporated by reference herein.
In FIG. 1, raw image data 106 captured on the focal plane array 108 is transferred to an ISP 110. The ISP 110 is used to convert the raw image data 106 into usable still or video images that can be stored, printed, displayed, or further analyzed. The ISP 110 runs various algorithms for this purpose. As an example, the ISP 110 may run one or more algorithms to perform various image processing tasks including, but not limited to: automatic dark reference, color filter de-mosaicing, white balance, color correction, color space conversion, and compression. The ISP 110 can be implemented by algorithms running on a standalone processor such as a Digital Signal Processor (DSP), algorithms running in a programmable semiconductor device such as Field Programmable Gate Array (FPGA), algorithms integrated directly into logic such as an Application Specific Integrated Circuit (ASIC), a combination of the aforementioned or other embodiments. Examples of ISPs are Faraday Technology Corporation's FTISP100S 2-Megal Pixel ISP, and Mtekvision's MV9313 ISP.
Processed image data 112 from the ISP 110 is then transferred to a system processor 114. The system processor 114 accepts user input 116 to control the zoom lens group and focus lens group, shown symbolically as two switches for zoom control, although it should be understood that a number of different user inputs may be delivered to the system processor 114 using a number of different input mechanisms to control different functions. The system processor 114 then generates control signals 118, shown symbolically as a focus control signal and a zoom control signal, although it should be understood that a number of different control signals may be generated by the system processor 114. These control signals are then sent to lens drive electronics 120, which control focus and zoom lens motor drives 122 within the lens module 100.
The focus and zoom lens motor drives 122 convert electrical energy to mechanical motion to move the zoom lens group 104 and the focus lens group 102, and may also control other functions of the lens module 100. For example, a motor drive can provide force to alter the position, shape, or location of other components within the image capture system. In another example, a motor drive can be used to change the shape and/or position of a liquid or pliable lens, change the physical position of a lens element, open or close a shutter (e.g. mechanically via an iris or optically via a transmission-variable Liquid Crystal Display (LCD)), or provide energy to an illumination source. Example embodiments include step motors, servo motors, screws, magnetic repulsion and attraction, piezoelectric, ultrasonic, flash, and the like. A motor drive can also comprise a knob, lever, gear, wheel, or other mechanical device or a combination of mechanical devices that can be moved manually or moved in combination with other motor drives. An example embodiment is a rotary knob that can alter the position of one or more lens elements to provide a focusing function. Motor drives can be made of multiple components, some of which can accept control signals from an ISP or other device that in turn translates these signals into the appropriate energy needed to provide the force to alter a property of an element. A simple example of a motor drive made of multiple components is a step motor driven screw. The screw drives a nut that is connected to the element of interest; when the screw turns, the position of the element changes. A motor such as a stepper is used to turn the screw. The motor requires energy to turn which is provided by a translator. The translator interprets control signals from the ISP or other source and converts these to electrical pulses of the correct relationship to turn the stepper motor. Another example is a liquid lens drive. The liquid lens has magnetic properties such that when one or more external magnetic fields are applied, the lens can change shape and/or position. The drive in this case can be a permanent magnet and/or a coil of wire. When the magnet is moved or the coil of wire is energized in varying ways, the changing magnetic field changes the properties of the liquid lens. A translator converts controls signals from an ISP or other device and converts these signals into the appropriate energy. An example of a liquid lens element is found in U.S. Pat. No. 6,369,954, the contents of which are incorporated by reference herein.
Because recent advances in focal plane array technology have enabled focal plane arrays to contain more circuitry and perform more functions, some conventional lens modules now incorporate the ISP 110 on the same integrated circuit chip that contains a focal plane array 108 such as a CMOS active column sensor. More advanced conventional lens modules 100 may also incorporate the processing of focus control on the same integrated circuit chip that contains the focal plane array 108.
However, as FIG. 1 illustrates, the electrical control signals 118 that control the zoom lens drives, the flash, the shutter and other functions though the lens drive electronics 120 (which convert electrical energy to mechanical motion to move the lens and control other functions) have conventionally been derived outside of the lens module 100. For example, an auto-focus control signal from a position measurement sensor (e.g. an infrared or ultrasonic sensor) may be derived in a discrete ISP 110 and sent to a focus drive within the lens drive electronics 120. For image-based focus control, the image data 106 must be transferred from the lens module 100 to the system processor 114 where an edge-detection auto-focus algorithm is used to develop the focus control signal. Additionally, the user may wish to manually alter the object distance by controlling the focus lens group 102. Signals from buttons, switches or other input devices must be input to the system processor 114 which in turn sends the appropriate focus control signals to the lens drive electronics 120. Control signals for the zoom lens group, flash, shutter and other functions are similarly generated outside of the lens module 100, as described above. An example of a conventional system with control signals developed outside the lens module is Published U.K. Patent Application No. GB 2,141,260 A.
Because conventional imaging systems utilize a lens module 100 separate from the devices that generate control signals, such as the lens drive electronics 120 illustrated in FIG. 1, additional manufacturing steps are required to assemble and connect the lens module together with these associated devices, increasing the time and expense of manufacture. In addition, these extra steps increase the chance of assembly errors.
Having lens modules separate from devices that generate control signals, such as the lens drive electronics, can also create performance issues. The generation of the control signals outside the module wastes system power because of the extra processing steps performed by the devices outside the module. In addition, as described above, imaging systems that have integrated auto-focus lens control utilize an algorithm for controlling the focus lens that is located on the ISP separate from the focal plane array. The image processor must read the image data from the focal plane array, process the data, and then transmit control signals to the drive electronics of the focus lens, increasing the image acquisition time.
Having lens modules separate from devices that generate control signals, such as the lens drive electronics, can also lead to undesirable product specifications and operational parameters. For example, the use of separate circuits (e.g. chips) for the lens drive electronics adds extra components, which can lead to increased imaging device size and weight. In addition, the use of separate circuits may require that each circuit be separately powered, with higher-powered output buffers used to drive signals between chips, resulting in increased power consumption.
In today's competitive consumer electronics environment in which the clear trends are increased features, decreased product size, and lower power consumption, manufacturers of imaging devices such as digital cameras and cell phones must utilize technologies which produce the most performance and capability in the smallest packaging possible, while at the same time minimizing assembly costs and the number of assembly errors.
With regard to capability, manufacturers would greatly benefit from a lens module with increased integrated functionality. An integrated modular approach would also allow imaging device manufacturers to make a standardized “platform” that can accommodate plug-in modules with different features to produce different product models.
With regard to performance, the size and power consumption improvements that can be realized using a lens module with increased integrated functionality would also be beneficial to imaging device manufacturers. Furthermore, compact compound zoom lens technology may be employed within these integrated modules, giving manufacturers a high-performance, wide-angle zoom lens not previously available in small imaging devices. Compact compound zoom lens technology is described in U.S. patent application Ser. No. 11/101,933, the contents of which are incorporated by reference herein.
With regard to minimizing assembly costs and assembly errors, manufacturers would greatly benefit from modularized multi-function components that enable devices to be assembled and connected with relatively few manufacturing steps, instead of having to assemble and connect multiple small devices.
Therefore, there is a need to integrate functions within a lens module, including some or all of the following: lens groups, lens motor drives, focal plane array, ISP, control of focus or object distance, zoom, flash, shutter, temperature compensation, and/or stabilization.